Dura-Vent Woodburning Chimney 15 Degree 8 Inch Galvalume Elbows is use to offset around obstructions such as rafters, ridgepoles, or joists. Dura-Vent elbow features a stainless steel outer casting with stainless steel inner wall and a twist-lock connection. Dura-Vent double-wall all-fuel chimney system is for use with wood stoves, fireplaces, furnaces, boilers, ranges, water heaters, or other appliances fueled by wood, oil, coal, or gas, and zero-clearance fireplaces that are factory-built.